SPRINGFIELD, Mass. (AP) – The owner of a Sunderland trout hatchery pleaded guilty Monday to killing herons and osprey that were feeding at his fish pools.

Michael Zak, 59, owner of the Mohawk Trout Hatchery, entered guilty pleas to two counts of violating the Migratory Bird Treaty Act and one count of conspiracy. Zak’s non-jury trial on two other charges – including allegations that he shot and killed a bald eagle – began before U.S. District Judge Michael Ponsor on Monday.

Zak could face up to three years in prison if convicted of all charges.

Zak’s attorney Vincent Bongiorni said his client acknowledged the killing of herons and osprey, but was not willing to accept a guilty plea for the eagle charge.

“There was a factual basis to support those two counts and our claim is that it doesn’t support the bald eagle count,” he said.

Zak and his employee, Timothy Lloyd, were charged last year with violating the Migratory Bird Treaty Act, which provides protection for migratory birds through international cooperation and treaties.

Federal investigators said they found more than 250 great blue heron carcasses, as well as carcasses of ospreys and a bald eagle on hatchery property. Tests showed the birds were killed by gunshots.

U.S. Fish and Wildlife Service agents say they staked out the hatchery periodically and saw Zak shoot at a heron with a scoped rifle and Lloyd shoot and kill an osprey.

Lloyd, 30, pleaded guilty Friday to two counts of violating the migratory bird act and one count of conspiracy. His sentencing was scheduled for June 27.